This invention relates to a method of controlling the molecular weight of polycarbonates prepared by the interfacial technique by adding certain metallic salts to the reaction media.
It is known from U.S. Pat. No. 3,035,020 that neutral inorganic salts such as sodium sulfate, sodium carbonate, potassium chloride, etc. can be added to an interfacial polymerization process to make aromatic polycarbonates from dihydric phenols and phosgene whereby the solubility of the organic phase and the water phase in each other is substantially lessened.
It is further known from the Russian Pat. No. 149,222 to Tarasov, et al. that sodium sulfite or sodium dithionite can be used in this same type of reaction to stabilize the dihydric phenol and thus prevent or lessen discoloration of the final polycarbonate resin.